1. Technical Field
The present invention relates to welding apparatuses and welding methods.
2. Description of Related Art
Conventionally, there have been known welding apparatuses that join two members by: applying electric current to the two members in contact with each other; melting materials of the two members adjacent to the contact surfaces of the two members by resistance heat generated at the contact surfaces; and pressing the two members against each other.
Japanese Patent Application Publication No. JP2007030013A discloses a welding apparatus that supplies electric current to a second member, which is inserted in a hole of a first member, so as to expand the second member by the Joule heat, thereby applying pressure to the interface between an inner wall of the hole of the first member and an outer wall of the second member. Then, the welding apparatus supplies electric current to flow through the first and second members via the contact surfaces thereof, thereby resistance-welding the contact surfaces.
However, since the welding apparatus disclosed in the above patent document applies pressure to the inner wall of the hole of the first member and the outer wall of the second member by thermally expanding the second member by supplying electric current thereto, there is a concern that a long time may be required to accomplish the resistance welding.